<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>formatNumber</title>
</head>

<body>
    <div>打开浏览器控制台查看结果</div>
    <script>
        const formatNumber = num => num.toLocaleString();
        console.log(formatNumber(123456));; // '123,456' in `en-US`
        console.log(formatNumber(15675436903));; // '15.675.436.903' in `de-DE`
    </script>
</body>

</html>